cregit-Linux how code gets into the kernel

Release 4.10 samples/kfifo/dma-example.c

Directory: samples/kfifo
/*
 * Sample fifo dma implementation
 *
 * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
 *
 * Released under the GPL version 2 only.
 *
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kfifo.h>

/*
 * This module shows how to handle fifo dma operations.
 */

/* fifo size in elements (bytes) */

#define FIFO_SIZE	32


static struct kfifo fifo;


static int __init example_init(void) { int i; unsigned int ret; unsigned int nents; struct scatterlist sg[10]; printk(KERN_INFO "DMA fifo test start\n"); if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) { printk(KERN_WARNING "error kfifo_alloc\n"); return -ENOMEM; } printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo)); kfifo_in(&fifo, "test", 4); for (i = 0; i != 9; i++) kfifo_put(&fifo, i); /* kick away first byte */ kfifo_skip(&fifo); printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo)); /* * Configure the kfifo buffer to receive data from DMA input. * * .--------------------------------------. * | 0 | 1 | 2 | ... | 12 | 13 | ... | 31 | * |---|------------------|---------------| * \_/ \________________/ \_____________/ * \ \ \ * \ \_allocated data \ * \_*free space* \_*free space* * * We need two different SG entries: one for the free space area at the * end of the kfifo buffer (19 bytes) and another for the first free * byte at the beginning, after the kfifo_skip(). */ sg_init_table(sg, ARRAY_SIZE(sg)); nents = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE); printk(KERN_INFO "DMA sgl entries: %d\n", nents); if (!nents) { /* fifo is full and no sgl was created */ printk(KERN_WARNING "error kfifo_dma_in_prepare\n"); return -EIO; } /* receive data */ printk(KERN_INFO "scatterlist for receive:\n"); for (i = 0; i < nents; i++) { printk(KERN_INFO "sg[%d] -> " "page_link 0x%.8lx offset 0x%.8x length 0x%.8x\n", i, sg[i].page_link, sg[i].offset, sg[i].length); if (sg_is_last(&sg[i])) break; } /* put here your code to setup and exectute the dma operation */ /* ... */ /* example: zero bytes received */ ret = 0; /* finish the dma operation and update the received data */ kfifo_dma_in_finish(&fifo, ret); /* Prepare to transmit data, example: 8 bytes */ nents = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8); printk(KERN_INFO "DMA sgl entries: %d\n", nents); if (!nents) { /* no data was available and no sgl was created */ printk(KERN_WARNING "error kfifo_dma_out_prepare\n"); return -EIO; } printk(KERN_INFO "scatterlist for transmit:\n"); for (i = 0; i < nents; i++) { printk(KERN_INFO "sg[%d] -> " "page_link 0x%.8lx offset 0x%.8x length 0x%.8x\n", i, sg[i].page_link, sg[i].offset, sg[i].length); if (sg_is_last(&sg[i])) break; } /* put here your code to setup and exectute the dma operation */ /* ... */ /* example: 5 bytes transmitted */ ret = 5; /* finish the dma operation and update the transmitted data */ kfifo_dma_out_finish(&fifo, ret); ret = kfifo_len(&fifo); printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo)); if (ret != 7) { printk(KERN_WARNING "size mismatch: test failed"); return -EIO; } printk(KERN_INFO "test passed\n"); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
stefani seiboldstefani seibold33478.96%125.00%
andrea righiandrea righi7718.20%250.00%
ira w. snyderira w. snyder122.84%125.00%
Total423100.00%4100.00%


static void __exit example_exit(void) { kfifo_free(&fifo); }

Contributors

PersonTokensPropCommitsCommitProp
stefani seiboldstefani seibold1493.33%150.00%
andrea righiandrea righi16.67%150.00%
Total15100.00%2100.00%

module_init(example_init); module_exit(example_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");

Overall Contributors

PersonTokensPropCommitsCommitProp
stefani seiboldstefani seibold38981.21%120.00%
andrea righiandrea righi7816.28%360.00%
ira w. snyderira w. snyder122.51%120.00%
Total479100.00%5100.00%
Directory: samples/kfifo
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